Photocatalytic oxidation of selected organic contaminants and inactivation of microorganisms in a continuous flow reactor packed with titania-doped silica

Two annular continuous flow reactors with nominal volumes of 400 mL and 150 mL were packed with silica gel pellets that were doped with titania (TiO ₂) (12 wt%). The reactors were configured with UV lamps in the center of the reactors. SOC oxidation experiments were performed in a single-pass mode with bicarbonate ions present and in a low dissolved oxygen environment. SOC concentrations decreased (ranging from 40% to 95%) without bicarbonate present. These removal efficiencies were not affected by moderate bicarbonate concentrations (up to 200 mg/L as NaHCO₃) or low dissolved oxygen levels (2 mg/L). Microbial experiments were performed for the inactivation of selected viruses and bacteria. The log [N0/N] values resulting from two hours of 254-nm UV irradiation for the bacteriophages X-174, PRD-1, and MS-2 were 1.67, 1.43, and 1.65, respectively. The log [N;bsubesub/N] values resulting from two hours of 254-nm UV irradiation for the bacteria Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa were 1.70, 1.40, and 1.62, respectively. In some instances experiments performed without pellets in the reactor produced greater inactivation, but in all experiments inactivation was below drinking water disinfection requirements.